The present invention relates to improvements in methods of and apparatus for forming and/or processing one or more streams of fibrous material of the tobacco processing industry, especially to improvements in a method of and in an apparatus for ascertaining the density of one or more wrapped or unwrapped streams of natural, substitute and/or reconstituted tobacco and for utilizing the results of density measurement or measurements to improve the quality of smokers' products, such as filter rod sections and plain or filter tipped cigarettes, cigars, cigarillos or cheroots.
A machine which is used for mass production of cigarettes or other rod-shaped articles of the tobacco processing industry is expected to turn out long series of rod-shaped articles which exhibit identical or practically identical properties as concerns their appearance, taste, weight, feel and resistance to the flow of tobacco smoke therethrough. This ensures that the purchaser of such articles is not annoyed by pronounced deviations of actual characteristics from desirable and accustomed characteristics of her or his brand of smokers' products. For example, a smoker expects that each and every article in a pack of plain or filter cigarettes will exhibit the same resistance to deformation by finger pressure, that each and every article will offer the same resistance to the flow of smoke from the lighted end toward and through the filter mouthpiece or directly into the mouth, and/or that the customary perforations in the wrapper of each article will admit identical quantities of cool atmospheric air. In order to ensure that all articles of a long series of articles which are turned out by cigarette making, filter tipping and like machines will exhibit identical desirable properties, it is necessary to continuously monitor at least some variable characteristics of the constituents of smokers' products and to continuously influence the manufacturing operation so as to eliminate the unwanted influence of variable characteristics upon the desirable parameters of the products. One of the variable parameters is the density of the stream of fibrous material which is draped into a web of cigarette paper, tipping paper or other suitable wrapping material in order to form a rod which can be subdivided into discrete plain cigarettes, cigars, cigarillos or cheroots of unit length or multiple unit length, into discrete filter rod sections of desired length or into discrete filter cigarettes, cigars, cigarillos or cheroots of unit length or multiple unit length.